1. Field of the Invention
The present invention relates to a method of manufacturing a dielectric film made of a dielectric material including a piezoelectric material, and to a method of manufacturing a liquid jet head including a piezoelectric element having a piezoelectric film made of a piezoelectric material.
2. Description of the Related Art
A piezoelectric element used in a liquid jet head and the like is an element formed by sandwiching a piezoelectric film made of a piezoelectric material exhibiting an electromechanical conversion effect with two electrodes. The piezoelectric film is made of a crystallized piezoelectric ceramic, for example.
Meanwhile, a typical liquid jet head using such a piezoelectric element is an inkjet recording head, which includes a vibration plate constituting part of a pressure generating chamber that communicates with a nozzle orifice for ejecting ink droplets, for example. This inkjet recording head is configured to deform this vibration plate by use of the piezoelectric element to pressurize ink in the pressure generating chamber, and thereby to eject ink droplets from the nozzle orifice. There are two types of inkjet recording heads which have been put to practical use, namely, an inkjet recording head applying a piezoelectric actuator of a longitudinal vibration mode configured to expand and contract in an axial direction of the piezoelectric element, and an inkjet recording head applying a piezoelectric actuator of a flexural vibration mode. As the inkjet recording head applying the actuator of the flexural vibration mode, there is known an inkjet recording head in which a uniform piezoelectric film is formed over an entire surface of a vibration plate by use of a deposition technique and then piezoelectric elements are formed independently for respective pressure generating chambers by cutting this piezoelectric layer into shapes corresponding to the pressure generating chambers by use of a lithography method, for example.
Meanwhile, a so-called sol-gel method is known as a method of forming a piezoelectric layer constituting a piezoelectric element. Specifically, sol made of an organic metal compound is coated on a substrate formed with a lower electrode thereon, and the sol is dried and gelated (degreased) to form a precursor film for a piezoelectric body. This step is performed at least once, and then the precursor film is subjected to a heat treatment at a high temperature and is thereby crystallized. The piezoelectric layer (a piezoelectric thin film) having a predetermined thickness is manufactured by repeating the above-described steps for several times (see Patent Document 1, for example).
According to the manufacturing method described above, it is possible to form a piezoelectric layer having a thickness of 1 μm or above, for example, relatively favorably, and thereby to prevent occurrence of cracks and the like. However, it is difficult to control a crystalline state of the piezoelectric layer such as grain size or orientation. Accordingly, the conventional manufacturing method has a problem in that a piezoelectric layer of desired characteristics cannot be obtained. Such a problem is not only limited to piezoelectric films made of piezoelectric materials for use in piezoelectric elements for liquid jet head and the like, but similarly exists in dielectric films made of other dielectric materials.
(Patent Document 1)    Japanese Unexamined Patent Publication No. 9 (1997)-223830 (pp. 4 to 6)